I see you noted the HW-8 and I agree. The 7, and 9 also. I include the OHR series of QRP rigs that have been around for a while and still available in kit form from an established firm. I suspect the FT-817, nd or non-nd, is going to be with us a while too. I have all three which constitutes my entire radio station.
In my opinion, if you are looking for longevity, the more modest the transceiver, the longer it will be operational and replacement components available. That includes rigs with the least micro-processing, SDR, DSP, and other doodads.
My opinion only.
72 Dick F8WBD